Writing image descriptions for graphs

Having completed my post-graduation and money filling my pocket, one day I remember sitting down and talking about stock markets to my friend who is visually impaired. Thinking about stock markets one would always think, let me research, invest and make more money. Browsing through various websites and trying to understand the graphs and then explaining it to my friend, it occurred to me how often we take graphs for granted. For us, it is usually very easy to quickly look at a graph and make complete sense out of it. Very often we forget that such graphs mean little or nothing to a person who is visually impaired. I thought to myself, if I would rely on graphs to understand the ups and downs happening in the stock market, how would my friend understand the same?

Soon a conversation with my friend made me aware of the various ways in which graphical data is made available to the visually impaired. She informed that to help a visually impaired better understand graphs, graphs are converted into tactile formats which are also known as “tactile graphs”. A tactile graph is read by touch rather than vision. Such graphs are created using various technologies. Tactile graphs should have a narration that guides the user in an orderly manner. The best way to do so, is to use legends. For example, the axes are represented by solid thick lines.

A second way to describe a graph is writing an alternate text (alt text). Alternate text conveys the information of a graph such as the title of the graph, the type of graph, the axes, and the trend of the graph which is read aloud by a screen reader. For the rest of the article, I will cover the broad idea of how graphs should be described using alternate text descriptions.

What are graphs?

Graphs are visual representation of data which explains the relationship between any two variables. They are often used to explain complicated and huge data without using much of text. In order to create a graph, a certain amount of data needs to be generated in the form of surveys or experiments.

The most crucial components of a graph are:

To select a graph that will be able to clearly represent the type of data generated.

The axes and scales, the horizontal axis (X-axis represents the independent variable) and the vertical axis (Y-axis represents the dependent variable).

A caption to the graph is equally important, as it conveys on what basis the graph is generated without giving any interpretation or conclusion about the data.

Now, based on the type of data generated there are many types of graphs available. Let’s talk about each type.

Pie chart – A pie chart represents the data in groups. The entire pie chart is split into slices according to the percentage of values. Pie charts are used when the number of groups are small, around 6 groups or less.

Bar graph – A bar graph is plotted using horizontal and vertical columns. The greater the length of the bars the higher values they represent. Example, the increase in the crop production each year. Generally, bar graphs are used when the differences between categories are larger.

Line graph – A line graph is like a scatter plot except that it makes use of a continuous variable, such as time, temperature, height, and weight along the X-axis. For example, the increase in weight of a person over weeks. Line graphs are preferred over bar graphs when the differences between categories are small.

Scatter plot – A scatter plot is generally used to explain the dependence/correlation between two variables. For example, the relationship between average rainfall and crop yields.

Understanding such complicated graphs poses a huge challenge for the visually impaired. The widely used method for this is relying on a screen reader to read aloud the text. At times, this can be quite difficult in case of complicated graphs and even 3D graphs. Broadly, alt text for any kind of graph should include the title of the graph, the type of graph, information regarding the X- and Y-axis, and the trend/information the graph is used to convey. A proper understanding of the data set and the purpose of the graph is a prerequisite for a person providing alternate text for graphs. For example,

A) Pie charts

Approach for writing alt text:

Here, we are describing a pie chart of the leisure activities performed in a day.

Tip: Even though a color key is provided, we do not mention the colors for each group as this information is not important. We begin describing the pie chart from the highest activity to the lowest activity performed.

Alternate text (Short description):

Pie chart displaying the percentage of various leisure activities performed by respondents in a day.

B) Bar graphs

Approach for writing alt text:

Here, we are describing a bar graph of the protein concentration in each fruit.

Tip: As we can see, the graph is described completely in the content below the graph. So, in this image, we begin describing the X-axis and the Y-axis followed by the fruit that contains the highest protein levels to the fruit with the lowest protein levels.

Alternate text (Short description):

Bar graph displaying the protein concentrations in grams across 5 different fruits.

Alternate text (Long description): Bar graph describing the protein concentrations in fruits. The X-axis shows the different fruits and the Y-axis shows the protein levels in grams ranging from 0 to 1.2 at an interval of 0.2 grams. The highest protein concentration was found in banana and the lowest protein concentration was found in apple.

Approach for writing alt text:

Here, we are describing a bar graph of the protein concentration in each fruit.

Tip: In case of this graph, there is no additional text given the protein concentrations. We provide all the information available in the graph including protein concentration for each fruit.

Alternate text (Short description):

Bar graph displaying the protein concentrations across 5 different fruits.

Alternate text (Long description): Bar graph describing the protein concentrations in fruits. The X-axis shows the different fruits and the Y-axis shows the protein levels in grams ranging from 0 to 1.2 at an interval of 0.2 grams. Apple has 0.3 grams of protein content, banana has 1.1 grams of protein content, pear has 0.4 grams of protein content, orange has 0.9 grams of protein content, and strawberry has 0.7 grams of protein content.

Additionally, the alt text can be provided in a table format as given in the line graph.

C) Line graphs:

Approach for line graphs:

Here, we are describing a line graph of the number of hours spent sleeping. We begin describing the X-axis and the Y-axis followed by the trend of the graph. We can approach this in three possible ways depending on the context of graph.

Alternate text (Short description): Line graph displaying the number of hours spent sleeping per day across 11 respondents.

Alternate text (Long description only explaining the trend):

Line graph describing the number of hours spent sleeping. The X-axis represents subjects and Y-axis represents time in hours at an interval of two hours. The graph shows a steady increase from Oliver to William and a gradual decrease from William to Sophie. The graph shows a steady increase from Sophie to Lissana with minor fluctuations. The graph ends with a steep decrease from Lissana to Wilson.

Alternate text (Long description explaining the trend as well as the values for each group):

A line graph describing the number of hours spent sleeping. The X-axis represents subjects and Y-axis represents time in hours at an interval of two hours. The graph shows a steady increase till 5, followed by another steep increase till 8. The graph continues to increase steadily till 10 and forms a peak at 11. The graph shows a steep decrease till 6, followed by a steady increase till about 7. It continues to rise and forms a peak at 8, followed by a gradual decrease till 5. The graph shows a steady increase forming another peak at 10 followed by a steep decrease till about 5.

Alternate text in Table format: The graphical data can also be presented in tabular format as shown below.

Subjects

Sleep (hours)

Oliver

3

Thomas

5

Emily

8

Isabella

10

William

11

Sophie

6

Robert

6.5

Smith

8

Jacob

7

Lissana

10

Wilson

5

Quick check list for writing graph descriptions:

Identify the type of graph, the title, the trend, the axes, and scale in every graph.

For a pie chart, the color of each slice or the color key is not important for the visually impaired. Providing correct values is more important.

A bar graph can be written as a short description, when the data is explained in the surrounding text. However, a long description or table may be opted depending on how much of the data is covered in the surrounding text.

Similarly, a line graph can be explained using only the trends, trends and all data points, or in a simple tabular format.

Here’s hoping that this blog gave you a brief idea of how to write graph descriptions! We would love to hear your own experiences and ideas, or you can even drop in a comment sharing your views.